U.S. Pat. No. 4,638,711 to Stroh discloses a locking mechanism for a floating vibrato bridge, i.e. a bridge which floats in a centered, generally horizontal position on a knife edge support under the opposing forces of the strings on the one hand, and a return spring on the other hand. When desired, a musician can move the bridge back and forth across the centered position by means of a vibrato arm attached to the bridge to produce a vibrato effect.
When no vibrato effect is desired, the bridge needs to be locked in the centered position so as to maintain the correct tuning of the instrument. This is conventionally done by parking the vibrato arm, i.e. pivoting it out of the playing position into a park position in which it locks the bridge.
Prior art devices had several drawbacks: for one, the locking mechanism required a close fit of the interlocking parts and was therefore prone to binding if the bridge was not prefectly centered when the arm was parked; and secondly, mechanisms intended to overcome this drawback were relatively complex and prone to misalignment.